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Topic: How does human evolution work? (Read 17472 times)

I think i have a grasp on the basics of evolution, so i have a question.

when a species allows for the survival of everyone, regardless of their genes (like ours), shouldnt it provide for the development of quick advances and changes in genes?Normally, for new traits to appear, it has to be beneficial to reproduction, or neutral to it. Then later a bunch of neutral traits can combine to form a positive trait.However in a society that allows for just about all traits to remain, then it opens up the possiblities, as potential negitives to reproduction (like ADD, for example) remain in the gene pool, instead of dying out. And later, a bunch of these can combine to make a sudden change...potentially...Idk its late...and im just thinking, not very coherently, but when am i ever really coherent...?

A mutation occurs and if that mutation allows the organism to be better suited to it's environment and survive when other organisms can't this this mutation will be passed down to it's offspring. Ultimately it's to pass on its genetic material but I would say that the "trait" benefits survival and then perhaps reproduction. I agree that some of the devlopments humans have made have slowed evolution down, it sounds bad but healing the sick is kind of slowing evolution down. That said new technologies will most like advance evolution, to use a media buzz phrase "designer babies".

Steven

In a time of universal deceit - telling the truth is a revolutionary act.

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another_someone

Firstly, evolution is about survival of the species, not survival of the individual. It is quite conceivable that an individual who is less able to survive on their own may actually in some cases benefit the species (for instance, it may makes them more dependent upon co=operation with others, which benefits the species as a whole even if it makes them personally more vulnerable – in many social insects, a lone insect is wholly incapable of surviving outside its social group, but it is the social group that works and not the individual).

Secondly, it is wrong to say that we do not have evolutionary pressures upon us. It is true that a far wider range of people are surviving, but actually there are probably far greater reproductive pressures than ever before (very many people today are surviving but not reproducing, or only minimally reproducing).

Thirdly, there are still sufficient wars going on that it will itself create local selective pressures.

Fourthly, to argue that a specific trait, such as ADD, is an evolutionary disadvantage is erroneous. You cannot say what traits are or are not evolutionary advantages or disadvantages – just because they may make your life easier or more difficult does not demonstrate that they will not prove in some wider and more subtle way actually to benefit the species as a whole – or maybe even the start of a new and more successful species – one cannot predict.

Sorry, last night i was realyl tired and just thinking randomly...BUt what i was saying sort of is related to Another_someones final statement.If a trait, which would normally cause the death of an individual in the wild, is now taken care of, and that individual survives, it gives the traits positive benefits a chance to reveal themselves.This allows for more genetic diversity in the species, as more traits and genes can survive.Im just curious how allowing for this increased number of traits will affect the outcome of humanity...

The outcome of humanity will depend much more on economy and society than on preserving weak genes or destroying them! A new world war or a famine plus plague or epidemics could zap away all the weak and defective genes in less than one generation.Nevertheless, biological diversity together with social and cultural differences should help the "global world" to go through this new millennium safely enough. Unfortunately we still remember recent and tragic experiments of "genetic cleanse" to reach the perfection in the human species.iko

just a thought...but isnt ADHD present in all children until about the age of 6ish, where most of them learn to control it?? just that if it is, surely it cant be called a faulty trait, or even a trait at all, just a failure on the brain's part to pick up on, and control?

"You have to stay in shape. My grandmother, she started walking five miles a day when she was 60. She's 97 today and we don't know where the hell she is."

We are still waiting for substantial evidence about ADHD: one defective gene? An abnormal enzyme? An environmental disease? A craving "intention to treat" by some?Haemophilia would fit much better as an example of genetic disease (heavy on the males affected by the severe type) that requires expensive treatment and can be transmitted to the next generation.As many other defects, it's rare enough and not a major problem for developed countries.Speaking of the "global society" and economy: just approx.20% of haemophiliacs are treated in this world, the other 80% survive and become crippled over the years (because of repeated and untreated bleedings in their joints).iko

but isnt this now less about evolution and more about adaptation?? seen as we dont seem to 'evolve' to conquer these defects, more like wait for science to conquer it. im not 100% on this, and a little drunk, so any backup would be nice lol

"You have to stay in shape. My grandmother, she started walking five miles a day when she was 60. She's 97 today and we don't know where the hell she is."

Wait wait wait...Evolution of a species means years and generations for a specific mutation to prevail (random mutation, then positive selection by the environment). Hundreds of years for humans, much less for insects.The famous brown butterflies didn't adapt to the smokey trees changing colour by themselves: in a short while all the white ones were easily spotted by birds, so the few brown "mutants" took advantage of this casual camouflage and survived over the years, replacing the whole "pool" of white butterflies.iko

Well we live in doncaster so we figure she's in greenland by now....i agree with what you say though, i laid in the grass on my lawn for 10 mins and didnt turn green.. so it MUST take years....although suspiously i wasnt attacked by birds either...

"You have to stay in shape. My grandmother, she started walking five miles a day when she was 60. She's 97 today and we don't know where the hell she is."

Probably the first mutant butterflies had just few darker spots in their wings...enough to prevail the white ones...Do you know the "story" of thalassemia and malaria? It is quite a good example of a defect that had been preserved instead of being eliminated through generations of people.I'll tell you this story if you are interested.

Your granny would freeze in Greenland, even walking all day!

iko

« Last Edit: 29/08/2006 09:45:13 by iko »

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another_someone

quote:Originally posted by ikoDo you know the "story" of thalassemia and malaria? It is quite a good example of a defect that had been preserved instead of being eliminated through generations of people.

Yes, I had heard about the use of the traces thalassemia leaves in the bones being used by archeologists to give an indication of the level of malaria that had been prevelent in the local environment.

Someone is alive around somewhere!Let me summarize thalassaemia and evolution (which we are discussing here).The most common thalassaemic "trait" (called beta-zero) is a genetic defect in synthetizing beta-chains for haemoglobin. Adult haemoglobin is composed by 4 sub-units proteins: two alpha chains plus two beta chains, each one with an iron molecule for carrying oxygen and carbon dioxide back and forth (all those iron bits give a red colour to the blood...am I clever?).Thalassaemia is an autosomic (not on X or Y chromosomes) recessive disease: if you have one defective gene on your pair, the other chromosome is doing the job and everything goes fine: you (actually me) are just a "carrier" (approx. 5% in the South of Italy).When two carriers decide to have kids they face these possibilities:25% will be perfectly normal (both chromosomes with ok genes), 50% healthy "carriers" like their parents, 25% sick children(both chromosomes with defective genes), unable to survive more than few years (now they are treated with transfusions and bone marrow transplantation in some). Those are just statistics, of course they might have 3 normal or 3 affected...but is much less probable.This is just to show how such a defective gene should be lost in normal conditions. In fact if there is a 25% loss each generation, any type of character tends to disappear quite soon.But the thalassaemia genes (and sickle cell haemoglobin too) are still well represented in areas of the globe where malaria epidemics had hit hard over the centuries (Italy, Greece, Turkey, Middle East, Africa).

The hypothesis is that the "carrier" condition, with its slight instability in the mechanisms of haemoglobin production, assemblying and red cells formation, does not represent an optimal environment for malaria parasites. Not a complete protection, just a decreased risk of successful infestation. Good enough to let survive some people, when all the village succumbed to a malaria epidemic.That is random-mutation, environmental selection, i.e. evolution.

25% will be perfectly normal (both chromosomes with ok genes), 50% healthy "carriers" like their parents, 25% sick children, unable to survive more than few years (now they are treated with transfusions and bone marrow transplantation in some).iko

This is my point though, medical science helps overcome these factors, not evolution!! im not tryin to contradict you in ANY way, (seen as im so far out of my depth, its like throwing a 2yr old into the deep end of a pool and expecting him to swim) but if we are using medicine to secure that even the people that in normal circumstances would die, are we not in fact tampering with evolution??....why is the basis of science contradiction? lol

"You have to stay in shape. My grandmother, she started walking five miles a day when she was 60. She's 97 today and we don't know where the hell she is."

quote:but if we are using medicine to secure that even the people that in normal circumstances would die, are we not in fact tampering with evolution??....why is the basis of science contradiction?weed4me

I see your point (It took me quite a while).In my personal opinion, maybe we find many more defective genes in our developed countries, compared to the 3rd world still endangered by starvation, epidemics (not only AIDS: in certain countries it is "normal" to carry several species of human parasites at the same time...) and wars. They have much better genes, like the Irish immigrants to the USA after decades of starvation (2x10E6 dead).But in what we'd call inhuman conditions, those selected genes help in surviving, not in living a life as we mean it.Wealth and technology allow people with more genetic defects to live a better life anyway. As far as I see all these healthy people around being in shape and getting older and older I do not worry so much about genetic defects increasing. It is a new world. It is up to us to defend it, protect it or destroy it.This is just my personal opinion of course.iko

quote:Haemophilia would fit much better as an example of genetic disease (heavy on the males affected by the severe type) that requires expensive treatment an can be transmitted to the next generation.As many other defects, it's rare enough and not a major problem for developed countries.Speaking of the "global society" and economy: just approx.20% of haemophiliacs are treated in this world, the other 80% survive and become crippled over the years (because of repeated and untreated bleedings in their joints).iko

Haemophiliacs grow up and have kids anyway.The ones treated in the world (20% in developed countries) do not suffer and have a normal life. All of them (100%) even the untreated and crippled ones preserve and transfer their defective genes. By special prenatal tests their wives (<20% in hyperdeveloped countries!) may know in advance if a male-fetus is haemophiliac or not. Some decide to have a child with their own defect. I can't blame them, here they do live a normal life.

quote:All of them (100%) even the untreated and crippled ones preserve and transfer their defective genes.

Not true, surely... I think quite a lot of untreated haemophiliacs die in childhood of otherwise minor injuries? Some make it to parenthood, but many don't... I'm sure the proportion of reproductively successful haemophiliacs is higher in the developed countries!

Surely the point is that at present we can (afford to) make it possible for more people with genetic conditions such as haemophilia and indeed many others to have children, so the genes which cause those conditions are more common amongst the next generation, and the next, and so on, than they would be if some or all of those affected by the condition died of it. So yeah, we're altering the path of evolution. Is that a bad thing? Well, we're certainly going to wind up increasing the dependence of society as a whole on "modern medecine"... which is fine if we assume that our current technologies ain't going to come crashing down round our ears (I've got an open mind on that one), but a bit tough on generations to come if at some point a wheel drops off and suddenly we can't afford the resources to keep all these people ticking over who will at best suffer very unpleasantly if those resources are withdrawn..

Equally, having converted some formerly strongly negative genetic traits into relatively minor inconveniences* we may find that at some point in the future the same trait that caused such a problem previously is exactly the get-out-of-jail-free card that the species needs to overcome some catastrophic change in conditions, allowing affected individuals to survive when the rest die out (personally I doubt that one'll be haemophilia but who knows..)

*I know, to some extent, whereof I speak... I was born with a cleft palate (probably not genetic, actually, but it can be genetically linked). I owe my continued existence to the cunning modern science of reconstructive plastic surgery or I'd have starved to death as a result of being unable to eat. Just an example of a potential catastrophe relegated to a minor inconvenience.

i always thought evolution was natural and was for the benefit of humankind on the whole, surely changing gentetics is not helping us evolve, but merely doing what humankind has been doing for so long...striving for perfection and immortality. yes i know, we wont acieve immortality through changing a few genes but still, by using medicical science to 'evolve' its more adaptation to achieve perfection rather than evolution no?

"You have to stay in shape. My grandmother, she started walking five miles a day when she was 60. She's 97 today and we don't know where the hell she is."

quote: i always thought evolution was natural and was for the benefit of humankind on the whole

Well, evolution's certainly natural, but it's no more "for the benefit of humankind" than gravity is.Some genes confer an advantage in a certain situation so not unnaturally the individuals with those genes breed more successfully, and so their offspring will have more and better opportunities.. continue for a number of generations and if the benefit the gene gives is strong enough its carriers will outcompete the rest (or become a whole seperate species) and evolution will have happened.Whether it benefits the species in the long term rather depends on how conditions develope... for example I read an article a bit ago that suggested that sexual selection for stupidly big antlers among some sort of Irish moose type animal resulted in the entire species dying out, the antlers having become unsustainable.

another_someone

I think the point people are missing here is that evolution is not the process by which things are changed, but the consequence of change and selection – the actual processes by which change and selection happen do not alter the reality of evolution, only its outcome.

Nor is evolution a particularly biological process – evolution applies as much to commerce (where some corporate entities dominate and others die off), and to political entities, and even to technology itself.

some genetic mutations, were this 10,000 years ago, or even 2000 would result in death, and a lack of offspring, therefore they would have died out.However now adays, those same mutations no longer result in death (because of medicine, science, etc) and the people with them can produce offspring before they die.So this gives those mutations a chance to produce benefits, when they survive, and possibly exist with other mutations whose combinations wouldnt have occured in the past

quote:All of them (100%) even the untreated and crippled ones preserve and transfer their defective genes.

Not true, surely... I think quite a lot of untreated haemophiliacs die in childhood of otherwise minor injuries? Some make it to parenthood, but many don't... I'm sure the proportion of reproductively successful haemophiliacs is higher in the developed countries!

Surely the point is that at present we can (afford to) make it possible for more people with genetic conditions such as haemophilia and indeed many others to have children, so the genes which cause those conditions are more common amongst the next generation, and the next, and so on, than they would be if some or all of those affected by the condition died of it. So yeah, we're altering the path of evolution. Is that a bad thing? Well, we're certainly going to wind up increasing the dependence of society as a whole on "modern medecine"... which is fine if we assume that our current technologies ain't going to come crashing down round our ears (I've got an open mind on that one), but a bit tough on generations to come if at some point a wheel drops off and suddenly we can't afford the resources to keep all these people ticking over who will at best suffer very unpleasantly if those resources are withdrawn..

Equally, having converted some formerly strongly negative genetic traits into relatively minor inconveniences* we may find that at some point in the future the same trait that caused such a problem previously is exactly the get-out-of-jail-free card that the species needs to overcome some catastrophic change in conditions, allowing affected individuals to survive when the rest die out (personally I doubt that one'll be haemophilia but who knows..)

*I know, to some extent, whereof I speak... I was born with a cleft palate (probably not genetic, actually, but it can be genetically linked). I owe my continued existence to the cunning modern science of reconstructive plastic surgery or I'd have starved to death as a result of being unable to eat. Just an example of a potential catastrophe relegated to a minor inconvenience.

i always thought evolution was natural and was for the benefit of humankind on the whole, surely changing gentetics is not helping us evolve, but merely doing what humankind has been doing for so long...striving for perfection and immortality. yes i know, we wont acieve immortality through changing a few genes but still, by using medicical science to 'evolve' its more adaptation to achieve perfection rather than evolution no?

"You have to stay in shape. My grandmother, she started walking five miles a day when she was 60. She's 97 today and we don't know where the hell she is."

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